A laser machining system for machining a workpiece uses a laser beam, preferably for cutting or welding a workpiece using a laser beam. The laser machining system includes a machining head with a housing having an opening for emitting the laser beam from the machining head, a measuring device configured to direct an optical measurement beam through the opening, and an optical unit for aligning the laser beam and the optical measurement beam, the optical unit being settable to adjust the laser beam and the optical measurement beam perpendicular to the optical axis of the machining head in the region of the opening. The measuring device is further configured to determine a setting of the optical unit corresponding to the central alignment of the laser beam on the basis of measurement values based on reflections of the optical measurement beam for different settings of the optical unit.